Although the existence of a round, hollow, geodesic sphere-shaped molecule consisting of 60 carbon atoms was first proposed by Kroto et al. in 1985 (Nature, Vol. 318, p. 162, 1985), it was not until 1990 that measurable amounts of this substance were prepared by Kratschmer et al. (Nature, Vol. 347, p. 354, 1990). This molecule was later named buckminsterfullerene or fullerene in honor of Buckminster Fuller, the inventor of the geodesic dome.
This form of carbon was obtained by resistive heating of graphite rods in an inert helium atmosphere. It is now known that fullerenes may be produced even from coal (Dance, I. G.; Fisher, K. J.; Willett, G. D.; Wilson, M. A. J. Phys. Chem., 95, p. 8,425, 1991), a cheaper alternative to the graphite process.
Besides the normally occurring carbon soot contaminants such as benzene, anthracene and other polynuclear aromatics, a variety of other different carbon complexes also form, including less round, yet hollow, molecules such as C.sub.32, C.sub.50, C.sub.70, C.sub.84, and other fullerenes even larger than C.sub.960 (Robert F. Curl and Richard E. Smalley, Scientific American, October 1991, p. 54-62). This new form of carbon complements the well known pyramidal shape of diamond carbon, and the hexagonal shape of graphite sheets.
By far the most abundant of all fullerenes in the raw soot are C.sub.60 and C.sub.70. However, fractional content of these compounds in the carbon soot obtained by any method can vary widely, and the fullerenes in the raw soot are normally recovered by either liquid extraction, sublimation or supercritical fluid extraction. Separation and recovery of essentially pure C.sub.60 can be achieved using Envirosep-ABC columns (ABC Laboratories, Columbia, Mo.) (Stalling et al., allowed U.S. Ser. No. 07/874,473 filed on Apr. 22, 1992).
Already, graphitized carbon is widely used in chromatography columns for separation of a variety of substances including antibiotic and other hydrocarbon isomers, PCBs and pesticides. The added uniformity and ordered structure of the carbon fullerene-as opposed to amorphous carbon graphite-may open avenues for developing even more powerful adsorbent, filtration, and chromatography matrices based on carbon. However, the fullerenes need to be attached to a support and form an insoluble matrix in order to provide a stable chromatographic phase. The support may be either liquid or solid, depending on the application.
Chromatography has been in widespread use for the fractionation, separation and analysis of biological and/or ecological materials. Various chromatographic techniques in use have included adsorption chromatography, ion exchange chromatography, gel permeation chromatography, gas chromatography, paper chromatography and thin-layer chromatography. In the ecological field, particularly, several of the same or different chromatographic techniques are often required to separate the complex mixtures of organic compounds encountered in laboratory samples to be analyzed.
It has occasionally been found that certain compounds or classes of compounds, when present in unknown mixtures, interfere with the normal separation and analysis of bioaffecting agents anticipated as being components of the mixture. For example, it has been very troublesome to completely separate toxic, planar polychlorinated biphenyl (PCB) components from mixtures which include other aromatic industrial chemicals together with pesticides, herbicides, natural biological fluids and fatty tissue. Moreover, the toxic, non-planar chlorinated aromatic compounds found as pollutants in the environment, such as P,P'-DDE and other pesticides, are typically difficult to chromatographically fractionate when found in admixture with certain planar components. Such non-planar pollutants are not retained by activated charcoal or other conventional adsorbents utilized in column chromatography. Separation and subsequent analysis has, however, been achieved by means of molecular size exclusion or gel permeation polymers. These materials are cross-linked copolymer gels which function like sponges on a micro scale. The size of the gel pores is controlled by the degree of cross-linking, and only certain molecular sizes penetrate the smaller pores of the gel. Other compounds of larger molecular size penetrate larger pores or are totally excluded.
The chlorine substituted naphthalene, dibenzo-p-dioxin and dibenzofurans have been found to be very hazardous to the environment because of their high toxicity to fish and animal life at concentrations well below one ppb. These planar, polynuclear aromatic compounds are preferentially adsorbed by passage through adsorption columns containing activated charcoal powders, often in admixture with dispersive agents or filter aids such as sand, magnesia, diatomaceous earth, and glass powder. Polyurethane foam has also been employed as an inert support for the carbon material in such columns. Such adsorbents are more fully discussed in U.S. Pat. Nos. 4,102,816 and 4,110,344 which issued on Jul. 25 and Aug. 29, 1978, to Stalling et al. However, such supports, dispersive agents, and filter aids do not enhance chromatographic separation and, consequently, a minimum of two columns are normally required for analyses where both planar and non-planar aromatics are suspected to be present in the sample.
Multiple chromatographic effects have been displayed in U.S. Pat. No. 4,303,529, by Huckins et al. through the utilization of powdered carbon or charcoal in admixture with a molecular size exclusion polymer as a packing media.